Section:
Getting Data from Point A to Point B
 Bittorrent
Host B
Router
Router
Router
Router
Router
Host A
Router
Router
 What are some advantages of this?
 Easy to set up and add nodes
 Scales well
 Partitioned system means faults are localized
 Many connections possible over the same line
 What are some disadvantages?
 Less direct paths
 Router processing power needed
(or specialized hardware)
Host B
Router
Router
Router
Router
Router
Host A
Router
Router
Host Q
Host P
Host A
Host B
 What are some advantages of this?
 Easy to keep networks separate and private
 Consistent response time
 Quality of Service
 What are some disadvantages of this?
 Doesn’t scale well
 Takes work to set up new circuits
 Unused network capacity common
 Virtual circuits
 Connection-oriented communication
 Like circuits, but delivered over packets
 Examples?
 Tor
 TCP
 Multiprotocol Label Switching
 Virtual circuit protocol
 Developed by Cisco
 For use inside networks
 Works on the link layer
 Labels added to link layer frames
 Routers very quickly look at, remove, and add labels
 Routing decisions using labels
 Traffic class field determines QoS priority
 Why do this instead of just using IP addresses?
 Why is this scheme problematic?
 Traffic can be routed according to priority
 Why might we want to prioritize traffic
differently?
 Traffic can also be rerouted dynamically
according to network conditions
 Examples?
 How could QoS be a problem?